In the production of hydrocarbon fluid from an earth formation, boreholes are drilled to provide a conduit for hydrocarbon fluid flowing from a reservoir zone to a production facility to surface. In conventional drilling operations the borehole is provided with tubular casing of predetermined length at selected intervals of drilling. Such procedure leads to the conventional nested arrangement of casings whereby the available diameter for the production of hydrocarbon fluid becomes smaller with depth in stepwise fashion. This stepwise reduction in diameter can lead to technical or economical problems, especially for deep wells where a relatively large number of separate casings is to be installed.
To overcome the drawback of a nested casing scheme it has already been proposed to use a casing scheme whereby individual casings are radially expanded after installation in the borehole.
WO 99/35368 discloses a method whereby casings of predetermined length are installed and expanded in the borehole. After installing and expanding each casing, the borehole is deepened further using a suitable drill string, whereafter the drill string is removed from the borehole. A next casing is lowered through the expanded previous casing section and subsequently expanded in the newly drilled borehole portion, etcetera.